// Package protocol defines the daemon/client control frames shared by
// transports. It intentionally contains data shapes only; app behavior stays
// in internal/app until the headless daemon split is complete.
package protocol

import (
	"encoding/json"
	"fmt"
	"time"
)

// FrameType identifies one protocol message kind.
type FrameType string

const (
	FrameHello          FrameType = "hello"
	FrameAuthChallenge  FrameType = "auth_challenge"
	FrameAuthOK         FrameType = "auth_ok"
	FrameAttach         FrameType = "attach"
	FrameDetach         FrameType = "detach"
	FrameProjectList    FrameType = "project_list"
	FrameChrome         FrameType = "chrome"
	FramePaneSnapshot   FrameType = "pane_snapshot"
	FramePaneChunk      FrameType = "pane_chunk"
	FrameLifecycle      FrameType = "lifecycle"
	FrameAttention      FrameType = "attention"
	FrameTrustPrompt    FrameType = "trust_prompt"
	FrameInput          FrameType = "input"
	FrameFocus          FrameType = "focus"
	FrameSwitchProject  FrameType = "switch_project"
	FrameOpenProject    FrameType = "open_project"
	FramePaletteCommand FrameType = "palette_command"
	FrameTrustResponse  FrameType = "trust_response"
	FrameResize         FrameType = "resize"
	FrameList           FrameType = "list"
	FrameStop           FrameType = "stop"
	FrameError          FrameType = "error"
)

// Frame is the transport envelope. Payload is deliberately raw JSON so
// network transports can frame without knowing every message type; loopback
// transports may pass the same bytes without JSON re-encoding.
type Frame struct {
	Type      FrameType       `json:"type"`
	RequestID string          `json:"request_id,omitempty"`
	Payload   json.RawMessage `json:"payload,omitempty"`
}

// NewFrame marshals payload into a protocol frame.
func NewFrame[T any](typ FrameType, payload T) (Frame, error) {
	b, err := json.Marshal(payload)
	if err != nil {
		return Frame{}, fmt.Errorf("protocol: marshal %s: %w", typ, err)
	}
	return Frame{Type: typ, Payload: b}, nil
}

// Decode unmarshals f.Payload into v.
func Decode[T any](f Frame) (T, error) {
	var v T
	if len(f.Payload) == 0 {
		return v, nil
	}
	if err := json.Unmarshal(f.Payload, &v); err != nil {
		return v, fmt.Errorf("protocol: decode %s: %w", f.Type, err)
	}
	return v, nil
}

type Hello struct {
	Version    int    `json:"version"`
	DaemonID   string `json:"daemon_id,omitempty"`
	ClientID   string `json:"client_id,omitempty"`
	ProjectKey string `json:"project_key,omitempty"`
}

type Attach struct {
	Token       string `json:"token,omitempty"`
	ProjectKey  string `json:"project_key,omitempty"`
	ProjectPath string `json:"project_path,omitempty"`
	TermSize    Size   `json:"term_size"`
}

type Detach struct {
	ClientID string `json:"client_id,omitempty"`
}

type Size struct {
	Cols uint16 `json:"cols"`
	Rows uint16 `json:"rows"`
}

type Project struct {
	Key        string    `json:"key"`
	Path       string    `json:"path"`
	Name       string    `json:"name"`
	LastActive time.Time `json:"last_active,omitempty"`
	TabCount   int       `json:"tab_count"`
}

type ProjectList struct {
	Projects []Project `json:"projects"`
}

type Chrome struct {
	ProjectKey string          `json:"project_key"`
	Model      json.RawMessage `json:"model"`
}

type PaneSnapshot struct {
	PaneID       string `json:"pane_id"`
	Bytes        []byte `json:"bytes"`
	Size         Size   `json:"size,omitempty"`
	DisplayOwner bool   `json:"display_owner,omitempty"`
}

type PaneChunk struct {
	PaneID       string `json:"pane_id"`
	Bytes        []byte `json:"bytes"`
	Size         Size   `json:"size,omitempty"`
	DisplayOwner bool   `json:"display_owner,omitempty"`
}

type LifecycleKind string

const (
	LifecycleSpawned      LifecycleKind = "spawned"
	LifecycleExited       LifecycleKind = "exited"
	LifecycleClosed       LifecycleKind = "closed"
	LifecycleStateChanged LifecycleKind = "state_changed"
)

type Lifecycle struct {
	Kind       LifecycleKind   `json:"kind"`
	ProjectKey string          `json:"project_key,omitempty"`
	ChildID    string          `json:"child_id,omitempty"`
	Child      json.RawMessage `json:"child,omitempty"`
	State      string          `json:"state,omitempty"`
}

type Input struct {
	PaneID string `json:"pane_id"`
	Bytes  []byte `json:"bytes"`
}

type Focus struct {
	PaneID string `json:"pane_id,omitempty"`
	Pad    string `json:"pad,omitempty"`
}

type SwitchProject struct {
	Key string `json:"key"`
}

type OpenProject struct {
	Path string `json:"path"`
}

type PaletteCommand struct {
	Kind string          `json:"kind"`
	Data json.RawMessage `json:"data,omitempty"`
}

type TrustResponse struct {
	ProcessID string `json:"process_id"`
	Preset    string `json:"preset"`
	Allow     bool   `json:"allow"`
}

type Resize struct {
	Size Size `json:"size"`
}

type Error struct {
	Message string `json:"message"`
}